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Cisco AutoQoS

Posted on 2014-04-16
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Last Modified: 2014-05-27
In Cisco Quality of Service, we can choose between IntServ and DiffServ.
However Cisco has a template called AutoQoS, once you run the AutoQoS command, it configures the quality of service for you.
What I need to understand , is which strategy AutoQos use ? does it use Intserv or DiffServ? if it uses neither , then how is the traffic classified ?

Thank you
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Question by:jskfan
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by:rauenpc
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ID: 40005117
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/auto_qos.html

This has some good info on AutoQoS, however, it will not directly answer your question.

DiffServ is the model used I believe. AutoQoS does not create any type of end-to-end bandwidth reservation which is what I understood Intserv to do. It simply defines a way to trust or untrust devices, and based on that it applies QoS markings and gives priority to packets as needed. This prioritization is local to the switch and once passed to the next device it's up to that device to treat the traffic correctly.
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by:jskfan
ID: 40006067
The way I see it is:
Inteserv = is like VMware Thick disk provisioning.
it carves out the bandwidth for a certain traffic and no other traffic can use that bandwidth, it is reserved.

Diffserv= is like Vmware Thin provisioning, for instance, traffic A can use 100Kbits, Traffic B 25 Kbits, Traffic C 60 Kbits. However if There is no traffic A , that 100 Kbits can be used by another traffic.


AutoQos= ???
I am not sure how it treats the traffic and the bandwidth
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by:rauenpc
rauenpc earned 300 total points
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AutoQoS certainly does not "thick provision" the switch. It just runs a long list of commands to ensure that the best practices defined on that switch with that code version are applied. It puts all the different cos and dscp values into different queues, sets up inbound traffic marking, and the switch in turn handles those markings based on the queues they are assigned. This will give traffic like voice priority, but there is no hard bandwidth reservation being set.
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by:jskfan
ID: 40008641
http://www.cisco.com/en/US/technologies/tk543/tk879/technologies_qas0900aecd8020a589.html

in the above link, they talk about AutoQoS and AutoQoS-VoiP.
Well AutoQoS-VoiP is clear , it ensures that VoiP traffic is efficient…
But it does not talk about AutoQoS , what traffic is prioritized first what is prioritized next, etc….

in other words, if throwing the command AutoQos is enough to make all types of traffic efficient, why would someone bother configure QoS for each specific traffic.
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by:rauenpc
rauenpc earned 300 total points
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AutoQoS is a way to easily provision your switches with a pre-defined set of values to support common scenarios - voice being the most obvious and promoted. However, every situation is different. You might need to put more emphasis on a specific application or a device. This is where you can configure QoS to give priority to whatever you want. In the work that I've done in the past, I've almost never needed to go outside the bounds of autoqos, but there were a couple times that I had to make a few custom rules for my customer to treat traffic differently than autoqos would.

In the end, it's always up to you to decide which method of QoS is best for your network.
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by:jskfan
ID: 40009906
But whether you use the AutoQos or you do not…you still cannot tell which traffic type you are favoring.

I believe the whole point that evolves around the Quality of Service, is to favoring one type of traffic over another…

There are hundreds of types of traffic( ftp,ipsec,pop,http,kazaa,gnutella,voice,etc….).
if you do not specify which traffic you are prioritizing, then how would you make a specific traffic efficient? AutoQos does not specify any traffic that will be prioritized…so i do not see the reason why it is used...
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Author Comment

by:jskfan
ID: 40010298
http://www.techrepublic.com/article/learn-the-benefits-of-cisco-autoqos/

I have done some reading in the above link, and what I concluded is, AutoQoS command is not used by itself, it is used with the traffic that you want to prioritize, example:

Router(config)# interface Serial0/0
Router(config-if)# auto qos voip
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by:jskfan
ID: 40017881
I wonder if that 's correct.
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by:Ruel Tmeizeh
Ruel Tmeizeh earned 200 total points
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Hi jskfan!
The auto QoS commands on Cisco equipment give a different config depending on the type of equipment the command is run on. The focus is on voice (RTP and signaling traffic), and Usually the config created will depend on external devices or PCs sending traffic that is marked with QoS values already. In other words, the auto QoS commands don't necessarily prioritize ANY traffic automatically, they usually setup proper CoS->DSCP mappings and such and setup the switch or router to trust traffic that is already marked for priority by a phone or other device. So if you need to prioritize particular types of traffic, based on the traffic type, rather than just trusting a PC or device, the auto QoS commands are a good starting point, but you will need to add additional commands to them to create the class maps that define the type of traffic (RTP, SIP, SCCP, SSH, HTTP, etc.) you are trying to prioritize, and apply those to the proper queues.
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by:jskfan
ID: 40067996
I have watched CBT Nugget video where the instructor mentioned that Typing Auto QoS command by itself will take care of the rest…
That was confusing and do not agree with it, this is why I posted this question to get a confirmation from other Experts.
To my understanding AutoQoS command is not used by itself, it is used with the traffic that you want to prioritize
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Ruel Tmeizeh earned 200 total points
ID: 40068906
Yes, generally that is the case that you would use it with other commands unless you just want to rely on priority markings from IP phones and such (which is a very basic scenario).
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by:jskfan
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Thank you Guys!
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